THURSDAY, Nov. 10, 2016 (HealthDay News) -- There's good news and bad news on smoking: Rates of smoking in the United States have tumbled to new lows, but health officials still estimate that four out of every 10 cancers is linked to the habit.

The latest report from the U.S. Centers for Disease Control and Prevention finds that cigarette smoking dropped from 21 percent of U.S. adults (45 million) in 2005 to 15 percent (37 million) in 2015.

But in a Thursday media briefing, CDC officials also stressed that as many as 40 percent of cancers may be related to tobacco use.

"Although smoking rates are at an all-time low, tobacco causes cancer of at least 12 parts of the body, accounts for three in 10 cancer deaths, and will kill 6 million current smokers unless we implement programs that help them quit," CDC director Dr. Tom Frieden said during the briefing.

The CDC notes that besides triggering lung cancer, smoking can also lead to tumors of the mouth and throat, voice box, esophagus, stomach, kidney, pancreas, liver, bladder, cervix, colon and rectum, as well as a type of blood cancer called acute myeloid leukemia.

In addition to cancer, smoking also contributes greatly to heart attacks, strokes and the majority of cases of COPD (chronic obstructive pulmonary disease), Frieden said.

According to another report released Nov. 10, every year between 2009 and 2013, some 660,000 Americans were diagnosed with a tobacco-related cancer and about 343,000 died from such a cancer.

Cancer accounted for three in 10 deaths among cigarette smokers, the report noted.

However progress has been made, Frieden said, and since 1990, about 1.3 million tobacco-related cancer deaths among Americans have been avoided.

"The smoking rate is almost a third of what it was in 1965," Harold Wimmer, president and CEO of the American Lung Association, added in a press release. "This is remarkable progress, and as a nation, we have seen some of the health benefits. However, tobacco use still accounts for an unacceptably high number of cancer diagnoses and deaths each year, especially lung cancer, which accounts for more than 126,000 deaths each year," he said.

And more and more people are either not taking up the smoking habit, or they are quitting, CDC researchers say. In fact, in just one year -- 2014-2015 -- the number of adults smoking cigarettes dropped nearly 2 percent.

The result: Cigarette smoking is now at its lowest since the CDC began collecting data in 1965, researchers said.

The CDC credits state tobacco programs for the continued decline in smoking. These programs focus on reducing cancer risk, detecting cancer early, improving cancer treatments, helping more people survive cancer, improving cancer survivors' quality of life, and better assisting communities affected by cancer, the agency said.

"Funding for these programs will yield a return on investment," Frieden said. "States that invest in these initiatives will reduce tobacco use that will result in fewer people with cancer, fewer deaths and reduced health care costs. It has been estimated that the annual cost of caring for an ex-smoker is $1,000 less than the annual cost of caring for a smoker," he said.

These programs also use strategies to prevent kids and young adults from starting to smoke. In addition, they help eliminate exposure to secondhand smoke, Frieden said.

"Progress across the U.S. has been inconsistent," he said. "There are large disparities among groups of people who use tobacco and in the groups affected by tobacco-related cancers."

According to the CDC, blacks still have the highest rate of deaths from smoking-related causes, compared with other groups, including those without a college education and people living in poverty.

Moreover, blacks are usually diagnosed later, when cancer is advanced, and they die earlier, Frieden said. This is related to the poorer quality of care many blacks receive, he said.

Among Americans, the Northeast has the highest prevalence of smokers, (202 per 100,000) and the West the lowest (170 per 100,000).

Rates for tobacco-related cancers are higher among men (250 per 100,000) than women (148 per 100,000), the researchers found.

According to Frieden, the FDA has approved seven different smoking cessation treatments, which can also double or triple the likelihood that a smoker who wants to quit will succeed, he said.

As for e-cigarettes, Frieden said scant evidence exists that they help smokers quit.

"We've heard stories of people who tell us they were able to quit using e-cigarettes -- that's a good thing," he said. "But no company has brought any e-cigarette to the FDA claiming that it can increase cessation rates. What we are seeing is that the majority of Americans using e-cigarettes continue to smoke."